Omnicom Group, 46%-owner of hot IPO stock Agency.com, set a 52-week high of $106 per share in a banner week for nearly all AdMarket 50 agency stocks. Agency.com stock nearly tripled in first-day trading. Also boosting Omnicom, and most other agency stocks, were bullish McCann-Erickson Worldwide forecasts for year 2000 ad spending. Of eight other AdMarket 50 agencies, seven also set new highs for the year. Only Grey Advertising did not. In trading Friday, Omnicom closed at $99.06, up 8.11% for the week.